NASICON-Structured NaTi2(PO4)3@C Nanocomposite as the Low Operation-Voltage Anode Material for High-Performance Sodium-Ion Batteries.

NASICON-type structured NaTi2(PO4)3 (NTP) has attracted wide attention as a promising anode material for sodium-ion batteries (SIBs), whereas it still suffer from poor rate capability and cycle stability due to the low electronic conductivity. Herein, the architecture, NTP nanoparticles embedded in the mesoporous carbon matrix, is designed and realized by a facile sol-gel method. Different than the commonly employed potentials of 1.5-3.0 V, the Na(+) storage performance is examined at low operation voltages between 0.01 and 3.0 V. The electrode demonstrates an improved capacity of 208 mAh g(-1), one of the highest capacities in the state-of-the-art titanium-based anode materials. Besides the high working plateau at 2.1 V, another one is observed at approximately 0.4 V for the first time due to further reduction of Ti(3+) to Ti(2+). Remarkably, the anode exhibits superior rate capability, whose capacity and corresponding capacity retention reach 56 mAh g(-1) and 68%, respectively, over 10000 cycles under the high current density of 20 C rate (4 A g(-1)). Worthy of note is that the electrode shows negligible capacity loss as the current densities increase from 50 to 100 C, which enables NTP@C nanocomposite as the prospective anode of SIBs with ultrahigh power density.